Win 8 to win 8.1 with boot camp again or to update?

can we easy update win 8x64 to win 8.1 via microsoft website,just finished win 8 installation over boot camp but i was wondering since microsoft is offering 8.1 on their site for free can we just update it like that or we need to find win 8.1 x64 iso file and start a new instalation over bootcamp again?
macbook air 2013

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